Kiruna Mine: The city of Kiruna is located in the extreme north of Sweden above the Arctic Circle and the city has grown up with mining.

With an ore body 4km long, 80m thick and reaching a depth of 2km, LKAB’s Kiruna is the world’s largest, most modern underground iron ore mine. Since mining began here over 100 years ago, LKAB has produced over 950Mt of ore, yet only one third of the original ore body has been extracted.

Since mid-1999, Kiruna’s haulage level at a depth of 775m has been replaced by the next level down at 1,045m, which will support production until 2018. The operation employs 1,800 people, of whom 400 work in the mine.

In 2006, Kiruna produced about two-thirds of LKAB’s total output of 23.3Mt, of which 16.9Mt were pellets. The company’s sales of iron-ore products also totalled 23.3Mt, of which 15.9Mt were pellets.

GEOLOGY: The Kiruna orebody was formed at around 1,600Ma following intense volcanic activity with the precipitation of iron-rich solutions on to a syenite porphyry footwall. The ore bed was then covered by further volcanic deposits (quartz porphyry) and sedimetary rocks before being tilted to its current dip of 50–60°. The ore contains a very pure magnetite-apatite mix, containing more than 60% iron and an average of 0.9% phosphorus. Black ore contains less apatite than grey ore.

MINING: The mine is divided into eight production areas, each containing its own group of ore passes and ventilation systems. Mining the ventilation shafts for the current production level was carried out by SIAB using Indau 500 raise borers, while Skanska Raise Drilling developed a total of 32 ore passes between the 775 and 1,045m levels using Tamrock and Robbins raise borers. Alimak developed two special units based on its RCM-6 system to reinforce the ore passes with cable bolts and shotcrete as necessary.

Ore is mined using sublevel caving, with sublevels spaced at 28.5m vertically. With a burden of 3.0–3.5m per ring, this yields around 8,500t for each blast. LKAB subsidiary Kimit AB supplies the explosives and prepares the holes for blasting.

The main haulage level at Kiruna lies at a depth of 1,045m, with the mine’s ore-handling systems capable of handling 26Mt/y of run-of-mine rock. Seven 500t-capacity shuttle trains, controlled from the 775m level, collect ore from ten groups of ore passes and deliver it to one of four crushing stations. -100mm ore is then skip hoisted in two stages to the 775m level and then to surface.

Remote Controlled Operations: As underground mining is known to have potential risks and hazards, Kiruna mine has obviated them by mechanizing all operations and establishing cent percent ‘automation’. Electric-powered, remote-controlled drilling and ore handling equipment supplied by Atlas Copco and Tamrock is widely used. After blasting, load-haul-dump machines (some of which are fully automated) carry the run-of-mine ore to the nearest ore pass, from which it is loaded automatically on to one of the trains operating on the 1,045m level.

After primary crushing, sampling using a Morgårdshammer automatic sampler to obtain the apatite and magnetite contents, and hoisting to surface, the ore is processed in Kiruna’s complex of a sorting plant, two concentrators and two pellet plants to give pellet and sinter fines products. Some ore is moved by rail to LKAB’s Svappavaara plant for pelletisation. Products are hauled by rail to the ports of Narvik (Norway) or Luleå for shipment.

Central Control: Loading, hauling and dumping on the sublevels are now fully remote-controlled from the control centre in the main office building on the surface. As a result, one operator can run three LHD loaders simultaneously, having to intervene only during loading, while the loaders can be operated continuously.

Remote control of loading and hauling poses another technical challenge – how to navigate a 14 meters long, 100 ton loader inside the mine? The solution is a system based on revolving laser on top of the loader, with reflectors located on the walls of the drives. Remote control also ensures that the machines operate for longer hours; there is no need to wait until dispersion of blasting fumes after detonation, and the machines need no coffee breaks!

Driver less Underground Trains: The first remote – controlled trains came into operation at Kiruna mine as early as 1970. Each train with one locomotive, and 24 mine cars hauls about 500 tonnes of ore, the train cycle being around one hour. Presently, six such trains are in operation at 1045 m level. Trains run 365 days a year. Crushing, weighing, skip loading and hoisting have been automatic for decades.

Besides streamlining mining operations, automation and remote control also contribute to better working conditions for staff, as there is no need for people to be in the zones where mining operation takes place.

The mine can be operated at night without a single person being down the mine!

Communication: Fibre optic cables connect key positions in the mine via feeder cables to other blocks. Each block is fitted with a base station for wireless communication which enables control and monitoring of different machines in the mine. Started in 1997, with wireless transmission of sound, images and data very fast Communication system has been established to enable operators to obtain information and have sufficient time to make proper corrections if needed.

Environment Friendly Mining: The ore mined in Kiruna is non-hazardous magnetite. An environmental management system, including environmental policy and reporting, is an important part of its total quality management system. “Cradle to grave planning” with due emphasis on environmental issues is taken into account in the initial stages of mine planning as well as when making new investments. Occupational health, environmental protection and energy efficiency are always considered when introducing a new technology.

Ventilation: As the mine is located north of the Arctic Circle, outdoor temperatures are close to or below zero degrees Celsius for long periods of the year. Therefore the air used for ventilation of the mine is first heated. This is done using surplus heat generated by the pellet plants, with periodic additional energy requirements being met by oil and electricity.

Air is passed through the mine at an average rate of 1000 m3 per second, which amounts to 34 billion m3 of air per annum. The return air from the mine is first passed through filters to remove particulate matter.

FUTURE PROJECT: The company is investing $925m in a third pelletising plant at Kiruna, with commissioning scheduled for 2008. The project also includes a concentrator and ancillary equipment. The world’s largest grate-kiln pelletising plant, KK4 will have an initial capacity of 5Mt/y of pellets, with the potential to increase its capacity to 6Mt/y.LKAB’s aim is to make Kiruna a ‘one-product’ operation, with the focus exclusively on pellet production. As a result, it is also investing in new flotation equipment for the Svappavaara concentrator, which will enable it produce pellet feed from some higher-phosphorus Kiruna ores. The project will provide around 1Mt/y of additional output through efficiency savings.

Note: Following mines are also known to be engaged in the production of iron ore by underground method of mining:

The Finsch diamond mine, located near Lime Acres, 160km northwest of Kimberley. Discovered in 1961 during exploration for asbestos, the deposit was first developed as an open pit. Since 1991, production has come from the underground mine beneath the old pit.

GEOLOGY: Finsch is a classic diamondiferous kimberlite pipe, which has a surface expression of around 17.9ha. The country rocks consist of banded ironstones overlying dolomites and limestones, the pipe itself consisting of weathered kimberlite (yellow ground) to a depth of around 100m with unweathered material (blue ground) beneath.

MINING AND BLASTING: The underground mine is accessed via a spiral decline from surface to the 680m level and a 9m-diameter, 763m-deep shaft equipped with three automatic Koepe hoists and capable of handling 5Mt/y of ore. Underground development began in 1978 and the shaft was commissioned in 1982.

The upper levels of the underground mine use a sub-level open stoping system. The ore and waste is moved from the production levels via vertical ore passes that feed the material to the crushers. The ore is then transported by belt conveyor to the shaft systems for hoisting to the surface. Production from the open-stope blocks 2 and 3 on the 430m and 510m levels below surface is being replaced by a block-caving system in block 4 on the 630m level that will reach full production of 3.8Mt/y of ore between 2007 and 2011. This will be depleted by 2015, with block 5 beneath following it into production in 2014.

Stope development utilises ore passes raise-bored to 2.9m diameter, then opened out to 6m diameter using a sliping rig that fits within the ore pass to drill the full profile. Semi-automated Tamrock drill rigs are used for drilling production rings in the open stopes. Rings consist of 102mm-diameter holes up to 45m long, through a full 360°. Dry drilling is used because of the weathering characteristics of the kimberlite.

Finsch makes use of specially developed, repumpable emulsion explosives, blended from components mixed underground and placed using dedicated transport and charging vehicles. The emulsion is sufficiently viscous to be pumped up 102mm vertical holes and to remain in position, and is inert until primed during charging. Benefits of this system include reduced carbon monoxide and nitrogen oxide emissions after blasting, and reduced explosive usage in fewer holes per ring. Detonation is controlled from the blasting cubicle in the underground production centre, with precise timing achieved by individually programmed microchip detonators.

12t-capacity LHDs dump broken ore into Finsch’s eight ore passes, each of which has a capacity of 10,000t. MMD sizers reduce the kimberlite to –300mm for transport to the shafts and hoisting to surface. In November 2005, Finsch started using an automated ore-transport system underground, costing US$18.5m to install. Centred on a specially built, high-speed, high-strength concrete road, 630m below surface, this marked a world first for underground mining in relation to fully automated trucking.

COMMUNICATIONS: Since 1988, Finsch has used an underground vehicle management and communication system. This was upgraded in 1995 to an El-Equip MultiCom radio-controlled data transfer system based on leaky feeder technology. The system permits multi-channel voice and data transmission. The position of LHDs underground is monitored using Modular Mining Systems’ dispatch system, the controller on surface instructing the individual machines where to load and dump through the mine-wide communications network.

Mount Isa Mines Limited (Xstrata Plc) operates two separate mining and processing streams, copper and zinc-lead-silver, at Mount Isa. Together the company’s 4 underground mines form one of the largest underground mining operations in the world. Discovered in 1923 with production commencing in 1931, Mount Isa is Australia’s and one of the world’s largest underground mining complexes.

Copper production at Mt Isa, Queensland, is derived from separate orebodies from those that form the basis for lead and zinc mining, with the copper operations being regarded as stand-alone operations.

Production currently comes from the 1,100 and adjacent 1,900 orebodies at the south end of the property and the deeper 3,000 and 3,500 orebodies below the lead mine in the north.

Copper mining: The years from 1969 to 1974 saw more expansion at Mount Isa Mines. Development of copper orebodies and improvements at the company’s Townsville refinery boosted copper production dramatically. The next surge of development came in the late 1990s when close to A$1bn was invested in various projects, including two new mines and an expansion of the copper smelter and Townsville refinery. Xstrata acquired Mount Isa Mines in June 2003 through its MIM Holdings Limited acquisition.

During the late 1980s, MIM started to develop the orebodies located between levels 21 and 36. A ramp was driven down from the U62 loading station and an ABB-Kiruna electric truck hoisting system fitted. Production started in 1993. In 1996, MIM launched the A$370m Enterprise Mine project designed to raise deep copper output to 3.5Mt/y.

The 713m-deep internal M62 shaft opened in 2000, with refrigeration and paste backfill plants completed in 2001. Meanwhile the 1100 operation became the X41 Mine. In June 2004, Xstrata approved development of the Northern 3,500 orebody to maintain rated capacity by supplying 5.3Mt ore grading 4.5% Cu over 11 years, starting in late 2006. This should enable the Enterprise mine to achieve its rated concentrator throughput of 3.5Mt/y.

Ore processing: The copper concentrator was rebuilt in 1973, with rod and ball milling and three-stage flotation, to supply the roaster and conventional blister copper smelter on site. In 1981, Mount Isa commenced anode casting as well. In 1988–89, two 6.4MW AG/SAG grinding mills replaced the rod and ball mills at a cost of A$35m.

With the development of Ernest Henry, MIM modified the pre-flotation, column flotation and slag-cleaning circuits to increase the plant’s throughput.

The flotation capacity was increased again in FY2003 with the addition of the latest-design Jameson cells. Smelter investments have included the copper IsaSmelt plant in 1994 and an expansion in 1998–99.

During 2004, Xstrata decided to add 40,000t/y of copper output by slag treatment and related developments, and also approved a 2,500t/y copper-leaching plant to treat smelter electrostatic-precipitator dust.

MIM established Copper Refineries Pty Ltd near Townsville in 1956 and started treating blister copper in 1959. Capacity has kept pace with the smelter at 260,000t/y, and was raised to 280,000t/y by mid-2006.

Ore production: Nearly 6mt ore was mined in 2008 from the two underground copper mines Enterprise and X41.

The copper smelter at Mt Isa has a current capacity of 300,000t\y. An extensive smelter emissions project is in progress to accomplish substantial decrease in emissions at Mt Isa by 2012.

The world’s new deepest mine was both safe and low-cost, AngloGold Ashanti vice-president Southern Africa Johan Viljoen said of the Mponeng gold mine in South Africa, which had broken through the 3 777 m depth level to create a global record.

Viljoen reported that the company had beaten the record held by Savuka gold mine, also an AngloGold Ashanti asset, for the past 28 years.

The cash costs at Mponeng were far lower than any other deep-level mine, as well as many shallow mines, proving, said Viljoen, that “deep can also be cheap”. He said the world’s deepest mine was producing gold at $222/oz.

Mponeng last year achieved a million fatality-free shifts and was runner-up in the fall-of-ground and the national safety campaign on low fatality, lost-time injuries and dressing cases.

With the current sink, the mine would go down to 4 100 m, which was another 300 m below the current record-breaking depth, and a prefeasibiity was under way for the Carbon Leader project, which would take Mponeng to 4 500 km below surface.

The North Antelope Rochelle Mine is one of America’s largest coal mines, producing the lowest sulfur coal in America. The complex shipped a record 97.5 million tons of compliance coal during 2008, and more than 1.2 billion tons since the mine began. Remaining coal reserves dedicated to the mine cover nearly 28,000 acres with about 1.2 billion tons of recoverable coal. The mine is located 65 miles south of Gillette, Wyoming.

Coal quality: The mine produces low-sulphur, sub-bituminous coal suitable for power station fuel without any preparation except crushing. Black Thunder coal has a heating value of 20.3MJ/kg, and the ash contents are around 5% while as-received moisture is 25–30%. The moisture content of some Powder River Basin coals increases their reactivity to the extent that spontaneous combustion can be a problem if they are not properly handled.

Mining and shipment: Black Thunder operates several individual open pits within its enlarged concession area, using five large draglines for overburden handling. The dragline fleet includes Ursa Major, the largest of the three, a Bucyrus-Erie (B-E) 2570WS model. The third-largest dragline ever built, it was assembled on site over a three-year period. Its 110m-long boom carries a 122m³ bucket.

Twentymile Coal Mine is one of the most successful coal production mines in the world. The coal mine is located 30km south west of Steamboat Springs in north-western Colorado, USA. It is the world’s most productive underground coal mine in terms of output per man-year. Coal from Twentymile has a high heating value of 11,350 Btu per pound and low sulfur and ash content, which makes it ideal for utility customers around the world.

Peabody installed a new Longwall system at the mine with the aim of increasing its output to 10.9Mt/y.

MINING METHOD: Twentymile uses a single Longwall as its main production unit. Its Longwall operation has one of the fastest, most powerful shearer in the world and Longwall panels that are more than 300 m wide. The shearer travels along the face at a speed approaching 40m/m, cutting 900mm of coal from the face at each pass. It typically completes 20–22 production cycles per shift, cutting at a rate of around 2,700t/h. Maximum daily (24-hour) output has been 46,340t. Computerised monitoring systems shut down the shearer to prevent the conveyor network from being overloaded if the face output rate approaches the conveyor’s maximum rating.

The geology of the mine calls for rock to be extracted along with the coal. Although not conventionally done, this prevents the rock-coal mixture from infusing with the coal. A specially designed conveyor system and chute was constructed to facilitate this process.

FUTURE PLAN: Peabody Energy and Twen­tymile Coal Co. could begin construction on the new underground Sage Creek Mine in West Routt County as soon as 2010. The new mine is anticipated to replace coal production at the existing Twentymile Mine when the underground Longwall mining operation runs out of coal sometime in 2013. The company is planning for a smooth transition to maintain consistent levels of production from one mine to the next

Bingham Canyon Mine, Utah (US) – This is supposedly the largest man-made excavation on earth. Extraction began in 1863 and still continues today, the pit increasing in size constantly. In its current state the hole is 3/4 mile deep and 2.5 miles wide.

Mirny Diamond Mine (Russia) – Supposedly the largest open diamond mine in the world at 525 metres deep with a surface diameter of 1200 metres; there’s even a no-fly zone above the hole due to helicopters reportedly being sucked in.

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2 thoughts on “Mines Visit”

Nice overview of famous mines, maybe you can split them into smaller articles or at least add a local links at the top of the page. It took me a while to go thru all that material. Have been in couple mines myself and it is interesting that most ore underground mines use different technology while coal mining is almost the same worldwide.